I am using the latest CodeBlocks revision 11703 together with wxWidgets f668f5b36f to play around with Fira Code and it doesn't work correctly, neither on Windows (Windows 10 1809) nor Linux (CentOS 7.6.1810 with MATE Desktop). The effects are slightly different though.
The good news: ligatures are working (when using Direct2D), the bad news: only the regular variant of Fira Code is working. All other variants (light, medium, bold, italic and its combinations) are not working in the editor. But they are working in the preview of the editor settings page (im not talking about the font selection dialog but the text left to the button to open it) and get applied to the line numbers.
In the editor however, something else happens, and for me this is different on Windows and Linux. If i select another variant on Linux it seems it is still using the regular variant, on Windows however for most variants it seems like a replacement font is used instead, only a few seem to use the regular variant.
For reference, on Linux in Eclipse all variants do work for me.